In the present embodiment, quantizer output values including variation values corresponding to duty errors of pulse width data (PWM output signals) occurring by the difference of the pull-down/pull-up drive characteristics (drive capabilities) of a buffer are stored in advance in a feedback value memory in a quantizer as feedback values FBV0 to FBV4, and a feedback value FBVn read out from the feedback value memory in response to the quantization of a delta-sigma modulation output is inputted into a subtractor by return input. Then, a quantizer output value including a variation value corresponding to a duty error is subtracted from input data Din, and delta-sigma modulation is performed such that the difference is minimized, whereby the duty error of pulse width data (PWM output signal) is compensated.